<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
:root {
  --size: 4.17vh;
  --main-color: #2B2B2B;
  --border-color: #fff;
  --jump-duration: 1s;
  --stairs-duration: 1s;
}

html, body {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

*, *::before, *::after {
  box-sizing: inherit;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background-color: var(--main-color);
}

.window {
  position: relative;
  width: 35.42vh;
  height: 50vh;
  background-color: #fff;
  border-radius: 17.7vh;
  border: 0.42vh solid var(--main-color);
  box-shadow: 0 0 0 1.25vh var(--border-color);
  overflow: hidden;
}

.window:before {
  content: "";
  position: absolute;
  top: calc(50% - 1.5vh);
  left: calc(50% - 0.5vh);
  border-radius: 50%;
  width: var(--size);
  height: var(--size);
  background-image: linear-gradient(to bottom right, #2E3691, #2E3691);
  box-shadow: 0.21vh -0.21vh 0.42vh 0.42vh rgba(0, 0, 0, 0.35),
  inset -0.31vh 0.31vh 0.21vh 0.1vh rgba(0, 0, 0, 0.75);
  animation: jump var(--jump-duration) ease-in-out infinite,
  gradientChange  12s infinite 0.5s;
}

@keyframes jump {
  0%, 100% {
    transform: translateY(-0.20vh);
  }
  50% {
    transform: translateY(-4vh);
  }
}

@keyframes gradientChange {
  0% {
    background-image: linear-gradient(to bottom right, #2E3691, #485A8B);
  }
  8.33% {
    background-image: linear-gradient(to bottom right, #485A8B, #9B2A89);
  }
  16.66% {
    background-image: linear-gradient(to bottom right, #9B2A89, #E6194D);
  }
  25% {
    background-image: linear-gradient(to bottom right, #E6194D, #F31C26);
  }
  33.33% {
    background-image: linear-gradient(to bottom right, #F31C26, #F27E1E);
  }
  41.66% {
    background-image: linear-gradient(to bottom right, #F27E1E, #FFC80D);
  }
  50% {
    background-image: linear-gradient(to bottom right, #FFC80D, #AFCA3E);
  }
  58.33% {
    background-image: linear-gradient(to bottom right, #AFCA3E, #15A14F);
  }
  66.66% {
    background-image: linear-gradient(to bottom right, #15A14F, #5B9E71);
  }
  75% {
    background-image: linear-gradient(to bottom right, #5B9E71, #54C6D3);
  }
  83.33% {
    background-image: linear-gradient(to bottom right, #54C6D3, #0CAAE3);
  }
  100% {
    background-image: linear-gradient(to bottom right, #0CAAE3, #2E3691);
  }
}


.stairs {
  position: absolute;
  width: 100%;
  right: -100%;
  top: 10.42vh;
  animation: stairs var(--stairs-duration) linear infinite;
}

@keyframes stairs {
  0% {
    transform: translate(0, 0);
  }
  100% {
    transform: translate(4.17vh, -4.17vh);
  }
}

.stairs span {
  position: absolute;
  top: calc(var(--i) * var(--size));
  right: calc(var(--i) * var(--size));
  width: 100%;
  min-height: var(--size);
  background-color: var(--main-color);
  border-bottom: 0.42vh solid var(--border-color);
  border-top-left-radius: 0.63vh;
}

</style>
</head>

<body>
  <div class="window">
    <div class="stairs">
        <span style="--i:1"></span>
        <span style="--i:2"></span>
        <span style="--i:3"></span>
        <span style="--i:4"></span>
        <span style="--i:5"></span>
        <span style="--i:6"></span>
        <span style="--i:7"></span>
        <span style="--i:8"></span>
        <span style="--i:9"></span>
        <span style="--i:10"></span>
    </div>
</div>
</body>
<script>

</script>
</html>


